Relay switching board in the KEL84 - World-Designs-Forum

Borats Baby · #1 9th January 2007, 04:20 PM

Hi, I'm new here so go easy on me....

Does anybody know where the htr+ and htr- wire goes to, from the relay switching board when fitted to the KEL84.. the instructions dont say..

Thanks

Rikki

Dave the bass · #2 9th January 2007, 05:34 PM

On the WD88VA they go across the +/- of the heater bridge rectifier. It's a 6.3 volt heater circuit, dunno it thats the same as the KEL84. The relay board operates on between 5-6 volts DC I've learn't today.

Have you phoned WD HQ, they're very helpful.

DTB

John Caswell · #3 9th January 2007, 11:17 PM

Hi all,
It is most important to get the supply to the relay board the correct way around otherwise you will poop off the diodes across the relay coils.
I have just had a look at the board and it is marked heater + and heater - so that should sort bit out.

John aka Dr John

Borats Baby · #4 9th January 2007, 11:22 PM

Hi all,

I think I've sussed the relay board out now.

New problem though

R1 is smokin on power up.........

I think I have been given the wrong rating, same happened to someone else I know who built one !

Also, the instructions I've got are for (I think) the older one with a tape switch. Mine has no tape switch fitted.....strugglin now to get the selector and volume pot wired in correctly as the instructions are for the 'non relay board' fitting.....

Any help ??

Mike G · #5 9th January 2007, 11:40 PM

Hi,

As DTB said in his post "Have you phoned WD?" They are very helpful indeed, and i'm sure if you have earlier instructions for the latest amp, they will sort the problem out for you.

I suspect many of us have earlier WAD KEL84's with the tape switch, but not that many BBer's will have seen the latest WD model.

I'd give them a call.

Mike.

petercom · #6 10th January 2007, 02:45 PM

Sorry you are having problems with this.

I've sent you the diagrams showing how the relay switch board heater supply is linked to the pcb.

In terms of the input switch and volume control, ignore the instructions for the 'wired' version and follow the relay switch board instructions. The input switch is connected using the multi-core cable to the relay switch PCB. From the relay switch PCB you take the Outputs to the volume control via a pair of screened leads.

We are in the process of completely rewriting the instructions but, as you can imagine, this is taking some time!

Borats Baby · #7 10th January 2007, 11:37 PM

Peter, I've sorted the relay board issue now, thanks for your help on that. However, I need your help re: R1.

I have removed one side of R1 (2.2K). I have seperated the power supply from the channel stages by removing resistors :

R6/7
R10/11
R12/13
R34/35

Also the 2 yellow wires to the output transformers. This has left the power
supply as a stand alone section, with no output load.

When I check at the choke, I'm getting 335 v dc, which shoud drop slightly when I reconnect R1.This looks good to me.

However, when I reconnect R1 to complete the power supply stage, R1 smokes badly (high current draw).

Before I start to remove and check the rectifying diodes/caps, I would like your feedback on this.

Any help would be appreciated.

Thanks

Rikki.....

petercom · #8 11th January 2007, 02:46 PM

That indicates a short, or partial short, after R1. The only components left in circuit are C3 and R38. Check that C3 is the correct orientation (the white negative bars on each capacitor C2 and C3 should be pointing towards the middle of the PCB) and that R38 is correct (red red yellow).

If those are OK then you need to track the problem down with your multimeter set to resistance, check across R38. With all components fitted the lowest reading you should get is 7.6 kOhms (depends which way round you put the clips, one way round it will be higher due to the capacitor).

I suspect you'll see a low resistance so remove the PCB and look for a solder bridge across tracks etc. You might also like to remove C3 to eliminate that as a possibility.

Give me a ring to discuss it if you like.

Borats Baby · #9 11th January 2007, 11:46 PM

Hello all.

Right,

On closer inspection of the board, C7 has NO track on either side of the board on the negative side.

Could this be why no matter what I do, R1 keeps smokin on power up ??

Could it be that I have a defective board ??

Rikki..........

petercom · #10 12th January 2007, 10:05 AM

Sounds like you have a defective board. Luckily the solution is simple without having to disassemble the PCB.

All you have to do is break one track and then make a link to C7. I'm e-mailing you a diagram so that you can see what to do.

Sorry that your PCB was 'wrong'. As you've probably seen commented elsewhere we inherited the WAD stock with very little documentation and, although we are doing our best to make sure all the components are up to our current standards, occasionally one error may creep through.

As we discover these, and thanks to everyone for their help and updates in spotting them, we're putting them right so everyone can get a 100% success rate on building their kits.

Well done for your investigate work and, once you've followed our correction, you should have a working amp.